Material web fixing device as part of a filter bag manufacturing installation

Abstract

A material web fixing device is used as part of a filter bag manufacturing installation. A material web transport device is used to transport at least two material webs, which fixed together at a distance from one another by at least one fixing seam, along a transport direction. A plurality of sewing units each have stitch forming tools configured as a sewing needle and a looper which interact with a thread. The material webs can be passed through between said stitch forming tools in the transport direction. An excess thread production unit is used to lengthen a thread path between the material webs. The excess thread production unit is arranged between the material webs in the thread run during operation. As a result, a material web fixing device is obtained, which allows filter bags to be produced with larger bag openings, particularly with larger opening extensions between the material webs.

The invention claimed is: 
     
       1. A material web fixing device as part of a filter bag manufacturing installation, comprising
 a material web transport device for the transport of at least two material webs to be fixed, by means of a fixing seam, at a distance from one another along a transport direction, 
 a plurality of sewing units with in each case one sewing needle and a looper acting as stitch forming tools between which the material webs can be passed through in the transport direction, the stitch forming tools interacting with a thread to produce the fixing seam, 
 an excess thread production unit to lengthen a thread path between the material webs, 
 the excess thread production unit being arranged in the thread run between the material webs during operation, 
 the excess thread production unit having in each case an oblique angled surface that lengthens the thread path relative to the transport direction, the oblique angled surface being arranged between the material webs during operation in such a way that it is passed over by the thread during seam formation due to the transport via the material web transport device, 
 with each sewing unit being associated to a respective one of the oblique angled surfaces. 
 
     
     
       2. The material web fixing device according to  claim 1 , wherein the excess thread production unit is configured as at least one sheet metal plate with a plurality of oblique surfaces, which a respective one of the oblique surfaces being provided for each sewing unit. 
     
     
       3. The material web fixing device according to  claim 2 , wherein the excess thread production unit has a plurality of sheet metal plates with a plurality of oblique surfaces each, with a respective one of the oblique surfaces being provided for each sewing unit. 
     
     
       4. The material web fixing device according to  claim 1 , wherein at least two oblique surfaces are oriented counter to one another such that the resulting forces applied by these oblique surfaces to the material webs in a direction transverse to the transport direction when passed over by the thread act in opposite directions. 
     
     
       5. The material web fixing device according to  claim 1 , wherein the excess thread production unit is adjustable between various default positions to define various thread path lengthening dimensions. 
     
     
       6. The material web fixing device according to  claim 1 , wherein the excess thread production unit is displaceable during the seam forming process. 
     
     
       7. The material web fixing device according to  claim 1 , comprising
 at least one additional excess thread production unit to additionally lengthen the thread path between two stitches of the fixing seam by an additional thread path, the additional excess thread production unit being arranged, during operation, outside the two material webs in the thread run facing the sewing needle, 
 at least one thread drawing unit to draw the additional thread path, which is first disposed outside the material webs, into the thread run between the material webs. 
 
     
     
       8. The material web fixing device according to  claim 7 , wherein the additional excess thread production unit, which is configured as a thread finger that is drivable to be displaced transversely to the transport direction, is arranged locally between the sewing needle in the top dead center and the material webs, wherein the thread finger is configured such as to initially lengthen the thread path during seam formation, wherein the thread comes out of contact with the thread finger once the thread path has been lengthened due to the transport via the material web transport device. 
     
     
       9. A method of fixing at least two material webs at a distance from one another, the method comprising the following steps:
 transporting the material webs along a transport direction to pass through between the stitch forming tools of a plurality of sewing units, 
 producing a fixing seam by means of the stitch forming tools by using a thread with a lengthened thread path, 
 lengthening the thread path of the fixing seam during seam formation by means of an excess thread production unit arranged between the material webs. 
 
     
     
       10. A filter bag manufacturing installation comprising
 a material web fixing device according to  claim 1 , 
 a sealing device for sealing the fixing seam formed in such a way that the material webs are permanently fixed at a distance from one another by means of the thread, 
 a material web edge joining device for closing side seams and/or bottom seam to form a ready-to-use filter bag.